New data shows that a genetic link does not exist between the giant short-faced kangaroo and the modern-day kangaroo and wallaby.

Dr Bastien Llamas from the University of Adelaide and other researchers made the discovery after analysing DNA extracted from the remains of giant kangaroos that roamed across Australia more than 40,000 years ago.

Previously, scientists relied on the information from bones to investigate the links between the ancient marsupials with modern-day kangaroos and wallabies.

Dr Llamas worked with small pieces of DNA extracted from specimens found in a cave in Tasmania and said there had been a long-running debate between scientists on the relationship between the giant short-faced kangaroos and the kangaroos and wallabies we know today.

"Morphologists for a long time have been debated about where to place those extinct guys [giant short-faced kangaroos]. Are they part of the modern diversity or are they another lineage on their own?" he said.

"There was quite a few questions still and fortunately with DNA we had enough information to tell you if it was a modern kangaroo or a bit different, or where it was in the [biological evolutionary] tree.

"The interesting bit is that what we find is that it's a lineage on their own. They didn't leave any descendents. They already [were made] extinct 40,000 years ago."

Dr Llamas said prominent palaeontologists Tim Flannery and Gavin Prideaux have debated over the links between the giant kangaroos, modern-day kangaroos and wallabies for around two decades.

But, according to Dr Llamas, research findings show there are no evolutionary links between the giant short-faced kangaroo and the banded hare wallaby, a species with ancient lineage that is related to all modern kangaroos and wallabies.

"We lost a complete lineage and then we have only one species surviving - the banded hare wallaby," he said.

"Apparently the genetic data is telling us that the sthenurine [the giant short-faced kangaroo] are not related specifically to the banded hare wallaby.

"We'd have this marsupial living off the coast of Western Australia, off Shark Bay - that is really the last survivor of a long living lineage. Sthenurines have disappeared."

Dr Llamas said that conservation efforts are underway to protect the banded hare wallaby, the genetic ancestor of all modern kangaroos and wallabies.

"There's a lot of people who have already done a lot of effort to manage and conserve that species, but definitely, it turns out that the banded hare wallaby is a very old lineage, basal to all the modern kangaroos and wallabies," he said.